1. Field of the Invention
This invention relates to evagination catheters which are used to obtain urine from the bladder for examination or drainage or to medicate the bladder. More particularly, it concerns evagination catheters that may be everted through the urethra into the bladder without vesical contamination. The invention also concerns methods for producing the new catheters.
2. Description of the Prior Art
Two methods are in general use for obtaining a sterile urine specimen or emptying the bladder, i.e., (a) catheterization and (b) suprapubic needle aspiration. Catheterization involves risk of vesical contamination, since relative movement of the outside of a standard push-in type catheter and the urethral mucosa can result in urethral flora being shoved into the bladder. If a catheter is introduced into the bladder without such movement, post-catheterization bacteriuria can be mitigated. Eversion of a catheter through the urethra avoids such relative movement, but problems of accomplishing such eversion in a clinically effective manner have impeded the utilization of this technique.
Although suprapubic aspiration avoids contamination problems, it is a much more difficult procedure and is avoided when possible.
The problem of maintaining sterility during intubation of the female urethra is discussed in U.S. Pat. No. 3,583,391. That patent discloses a catheter device in which a cot portion may be everted in such a way that movement does not take place between the outer surface of the cot and the urethal mucosa. The device is an outgrowth of an earlier everting cot of Helmholz, J. Urol., 64: 158 (1950). Other devices utilizing the principle of an everting cot or tube are disclosed in U.S. Pat. Nos. 3,332,424; 3,506,011; 3,589,356 and 3,669,099.
The evagination catheter of Cox et al (U.S. Pat. No. 3,583,391) requires a push catheter to accomplish the evertion of the cot through the urethra. The elimination of this push catheter is desirable. Thus, it presents a possible source of injury during evagination and difficulties are encountered in connecting the tip of the push catheter to the distal end of the everting cot.